Journal of the American Mosquito Control Association, l8(3):138-151, 2002The copyright of the publication does not extend to this article.

MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATINAMERICA-A TWELFTH SYMPOSIUM

GARY G. CLARK' INO HUMBERTO QUIROZ MARTiNEZ' (ORGANIZERS)

ABSTRACT. The 12th annual Latin American symposium presented by the American Mosquito ControlAssociation (AMCA) was held as part of the 68th Annual Meeting in Denver, CO, in February 2OO2. Theprincipal objective, as for the previous 11 symposia, was to promote participation in the AMCA by vectorcontrol specialists, public health workers, and academicians from Latin America. This publication includessummaries of 35 presentations that were given orally in Spanish or presented as posters by participants from 7countries in Latin America. Topics addressed in the symposium included results from chemical and biologicalconftol programs and studies; studies of insecticide resistance; and population genetics, molecular, ecological,and behavioral studies of vectors of dengte (Aedes aegypti and Aedes albopictus) and other arboviruses, malaria(Anopheles albimanus and Anopheles pseudopunctipennis), leishmaniasis (Lutzomyia), and Chagas Disease (Zrl-atoma). Related topics included biology and control of Culiseta inomata, Ochlerotatus taeniorhynchus, scor-pions, Chironomus plumosus, and Musca domestica.

KEY WORDS Mosquitoes, mosquito control, bionomics, Aedes, Anopheles, Culiseta, Ochlerotatus, Lutzo-myia, Triatoma, scorpions, Loxosceles, Musca domestica, Chironomus, insecticide resistance

INTRODUCTION

The American Mosquito Control Association(AMCA) is dedicated to the study and conrrol ofmosquitoes, other vectors, and other arthropods andpromotes cooperation and interaction among pro-fessionals and students in this field both in the USAand internationally. To promote greater and moreactive participation among and with a portion of itsinternational membership, a Spanish language sym-posium was held lst at the AMCA Annual Meetingin l99l and at all subsequent meetings. In additionto providing a forum for scientists whose primarylanguage is Spanish, the session promoted interac-tion and esprit de corps within this group; interac-tion with control industry representatives; and in-teraction with professional colleagues in the USAwho are involved in mosquito vector control, train-ing, and research at the university level, and withstate and federal government officials.

This publication includes summaries of 35 pre-sentations that were given in Spanish by partici-pants from 7 countries in Latin America. Topicsaddressed in the symposium included results fromchemical and biological control programs and stud-ies; studies ofinsecticide resistance; and populationgenetics, molecular, ecological, and behavioralstudies of scorpions, Chironomus plumosos, andMusca domestica, and vectors of dengue (Aedes ae-gypti) and other arboviruses, malaria (Anopheles al-b imanu s and Ano p he I e s p s e udo p un c t i p e n n i s), leish-maniasis (Lutzomyia), and Chagas Disease(Triatoma). Other subjects included biology andcontrol of Culiseta inornata and Ochlerotatus tae-niorhychus. Summaries of 10 previous symposia

I Dengue Branch, Centers for Disease Control and Pre-vention, 1324 Calle Caflada, San Juan, PR 00920-3860.

'�Laboratorio de Entomolog(a, Facultad Ciencias Biol-6gicas, Universidad Aut6noma de Nuevo Le6n, San Ni-col6s de los Garza, Nuevo Le6n, Mdxico.

have been published (Clark and Suarez 1991,1992,1993; Clark 1995, 1996; Clark and Rangel 1997,1998, 1999; Clark et al. 2000; Clark and Quiroz-Mart inez 2001).

Financial support for this session was providedby the following sponsors and individuals: ClarkeMosquito Control Products (Lyell Clarke III), H. D.Hudson (Manuel Lluberas), Vopak (BenjaminGomez), Wellmark (Larry Smith), RockefellerFoundation, and the Pan American Health Organi-zation. Funds from these sponsors provided AnnualMeeting registration and partially defrayed travelexpenses for many symposium participants. Enthu-siasm and interest for this symposium among Span-ish- and non-Spanish-speaking participants washigh and it will continue to be a part of future meet-ings.

SUMMARIES

Characterization of anopheline breedinghabitats in the Upper Orinoco River,

Amazonas State. Venezuela

Yasmin Rubio-Palis, Crist6bal Menare,Andr6s Quinto, Magda Magris, Manuel Amarista

and Alfredo Gutilrrez

Centro de Estudios de Enfermedades Enddmicas ySalud Ambiental, IAESP "Dr. Arnoldo Gabal-

don," MSDS, Maracay, Venezuela: Direccitjn Re-gional de Salud, Endemias Rurales, Amazonas;

Centro Amaz6nico de Investigaci6n y Control deEnfe rmedade s Enddmicas ( CAIC ET ), Amazonas,Venezuela; antl Laboratorio de Malacologia, In-

stituto Pedro Kouri. La Habana. Cuba

Between October 1999 and January 2000,anopheline breeding habitats were identified andcharacterized in Ocamo area, Municipality of Up-per Orinoco, Amazonas State, in southern Vene-zuela. During the study, 46 samples were taken

t 3 8

SBprsMsBn 2002 MosOurro Vecrop Covrnol AND Brolocy rN LlrrN AT4ERICA-A TwsI-FrH Swtposrur.t 139

from 4 types of larval habitats: lagoon (37),ponds (2), pools ( l) , and streams (6). Anophelinelarvae were present in 38 of the habitats sampled.A total of 1,303 anopheline larvae were collect-ed, belonging to 7 species: Anopheles oswaldoi,An. darlingi, An. triannulatus, An. mattogrossen-sis, An. punctimacula, An. mediopunctatus, andAn. braziliensis. Not all of the larvae collectedwere identified to species because many lst and2nd instars failed to reach the 4th larval instar oradults. The most abundant and frequent speciescollected was An. oswaldoi, followed by An.triannulatus and An. darlingi. The remaining spe-cies accounted for lOVo of the collections. La-goons were the most productive breeding sites interms of the total number of larvae collected(1,O34) and species diversity, although densitywas low (0.59 larvae/liter). The biotic and abioticfactors that influenced the species collected weredetermined by an analysis of canonic correspon-dence (CANOCO). The biotic factors analyzedwere type of vegetation, percentage of cover, andanopheline larval instars collected, whereas theabiotic factors considered were type of larvalhabitat, water depth (cm), pH, temperature ("C),shade, and water permanence (permanent vs.temporal). The CANOCO showed that waterdepth signif icantly determined species abun-dance, whereas pH and water temperature had lit-tle effect. Anopheles triannulatus was found indeeper waters, whereas An. darlingi, An. oswal-doi, and An. mattogrossensis were found in shal-lower sites. Regarding species association withbiotic factors, a positive association was foundbetween An. triannulatus, An. darlingi, and An.mattogrossensis and 4 variables: pupal density,larval density, submerged vegetation, and float-ing seeds. On the other hand, these speciesshowed a negative relation with 4 other variables:shrubs, floating vegetation, algae, and grasses.

Bionomics of Anopheles mosquitoes in malariaresidual foci of Oaxaca, M6xico

Mauricio Casas, M., Juan I. Arredondo-Jim€nez,Nelba Chirino and Mario H. Rodrfguez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas,

Mdxico; and Centro de Investigaciones Sobre En-fermedades Infecciosas, Instituto Nacional de Sal-

ud Ptiblica, Cuernavaca, Morelos, Mdxico

We conducted studies on the bionomics ofAnopheles mosquitoes in malaria foci of Oaxaca,M6xico. Few studies, if any, have been carriedout in the area, so more knowledge on the dy-namics of mosquitoes was needed. Fluctuationsin mosquito population densities, larval habitats,host-seeking behavioq and feeding patterns wereassessed between July 2000 and June 2OOl in 2coastal villages and 2 mountainous villages.

Three species of anopheline malaria vectors werecollected on humans or mammals. In coastal vil-lages, collections yielded Anopheles albimanus(93-97 Vo), An. p s eudop unctip e nnis (l-1 Vo), andAn. punctimacula (2Vo), whereas mosquitoesfound in villages of the foothills area were An.p s e ud op unc t i p e nni s (9O -99 7o), An. p unc t imac ul a(8Vo), and An. albimanus ( l-27o). Anopheles al-bimanus was active throughout the night, show-ing a significant increase in biting rate beforemidnight, whereas the An. pseudopunctipennisbiting peak occurred after midnight during thewet season in villages located at a lower eleva-tion. Blood-meal analysis indicated that goats(38.7Vo) and humans (35.5Vo) were most pre-ferred by An. albimanzs in coastal villages,whereas <47Vo of female An. pseudopunctipenni.sand l}OVo of An. punctimacula fed on a horse inthe same area. Both horses (2O.6Vo) and dogs(2O.6Vo) were selected by An. pseudopunctipennisover human hosts (10.770) in villages in the foot-hi l ls.

Biological Yariation amongAnopheks vestitipennis populations in

southern M6xico

Armando Ulloa, J. I. Arredondo-Jimenez,M. H. Henry-Rodriguez and I. Fernandez Salas

Centro de Investigaci6n de Paludismo, INSP, Ta-pachula, Chiapas, M€xico; Centro de Investiga-ciones Sobre Enfermedades Infecciosas, 1NSP,

Cuernayaca. Morelos: Laboratorio de Entomolo-gia Mddica, Universidad Aut6noma de NuevoLe6n, San Nicokis de los Garza, NL, Mdxico

Studies that used genetic and egg ornamentationof populations of Anopheles vestitipennis revealedthe possible existence of distinct anthropophilic andzoophilic sympatric populations. In this study, wecompared the length of the gonotrophic cycle, sur-vival, and the oogenic development of both popu-lations. The study was carried out in Nueva Inde-pendencia, Chiapas, in southern M6xico.Mosquitoes were collected with sets of 2 traps bait-ed either with 2 men or a horse between l8O0 and24OO h. The gonotrophic cycle was estimated witha cross-conelation analysis, whereas the survivalrate was assessed with a vertical method. Dailychanges of parity rates gave significant correlationindices at 3 days (r : O.292, P < 0.001) and 4 days(r:0.918, P < 0.5) in the zoophil ic and anthro-pophilic populations, respectively. The survival ratewas 0.93 and 0.88 and the minimum time requiredto develop mature eggs after bloodfeeding was 54h and 60 h in females from zoophilic and anthro-pophilic populations, respectively. Differences ob-served in these biological parameters provide ad-ditional support for the possible existence ofsubpopulations with distinctive feeding preferenceswithin An. ve stitipennis.

140 IounNer- op rue AneRrcex Moseurro Conrnol AssocrATroN Vor-. 18, No. 3

Field evaluation of Agnique MMF@ to controlAnopheles albimanus, a malaria vector, in

Chetumal, Quintana Roo, M6xico

Marco A. Dominguez-Galera, Mario Urzua,Adriana E. Flores-Suarez and

Ildefonso Fernandez-Salas

Programa de Control de Vectores, Secretaria deSalud, Mdxico; and l-aboratorio de Entomologia

Medica, Facultad de Ciencias Biologicas, Univer-sidad Aut6noma de Nuevo Le6n, San Nicolas de

los Garza, Nuevo Le6n, Mdxico

The Malaria Control Program in Quintana RooState has relied in recent years on the followingactivities: wall spray with Deltamethrin WP, ul-tra-low-volume space-spraying with permethrin,l iquid Temephos (507o) against larval popula-tions, and infrequently, cleaning of green algaein vector breeding sites. Beginning in 2000, thestate malaria control program started evaluatingproducts that were less toxic to the environmentand human health. The program tested AgniqueMMF@ as a potential choice against larval andpupal populations of Anopheles albimanus (Wie-demann). Agnique MMF produces a monomolec-ular film that acts on all aquatic instars of Culic-idae. Agnique MMF reduces water surfacetension at the air-water interface, thus suffocat-ing larvae and pupae, which drown and sink tothe bottom. Newly emerged male and femalemosquitoes also drown. Oviposit ing females st ickto the water surface and die. To evaluate its ef-fectiveness in reducing immature and adult stagesof An. albimanus, Agnique MMF was evaluatedin the field by using a Hudson X-pert backpackto dispense the material at a rate of 4.7 liters/ha.Larval densities were measured 3 days beforetreatment with 100 dips per day and for 15 daysafter treatment. We found that larvae started dy-ing 24-48 h after applications, with 10070 mor-tality at 72 h. Human landing collections record-ed the impact of Agnique MMF on adult An.

albimanus populations. Landing collections by 2collectors were performed for 15 days after treat-ment and a 6OVo reduction of female mosquitoeswas found compared to the untreated area.Changes in age structure of females confirmedreduction of older individuals with an increase ofnullipars from3TVo before treatment to

"72Vo aftertreatment. The untreated area located 2 km awayhad results similar to the pretreatment period. Be-cause of the prolonged2L-day residual effect andsafety to nontarget aquatic organisms, AgniqueMMF was incorporated as a new tool for controlof larval An. albimanus in the Quintana Roo Vec-

tor Control Program.

Large-scale evaluation of Vectobac@ AS andVectolex@ CG for the control ofAnop hele s p s e udop unctip e nnis in

Oaxaca, M6xico

Juan I. Arredondo-Jim€nez, Mauricio Casas andMario H. Rodrfguez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud PrtbHca, Tapachula, Chiapas,

Mdxico; and Centro de Investigaciones Sobre En-

fermedades Infecciosas, Instituto Nacional de Sal-ud Prtblica, Cuernavaca, Morelos, Mdxico

A large-scale study was carried out during thedry seasons of 2000 and 2001 to evaluate the im-pact of 2 bioinsecticides, VectoBac@ AS (Bacillusthuringiensis israelensis) and Vectolex@ CG (Ba-cillus sphaericas) on larval and adult populationsof Anopheles pseudopunctipennis in Oaxaca, M6x-ico. Experimental areas included 3 groups of 3 vil-lages, with each group corresponding to I treatmentand I control. Larvicide was applied with handcompression pumps (2000) or mist blowers (2001)on all water sites located within a 1.5-km radiussurrounding each group of villages, at rates of 4liters/ha (VectoBac) or ll.2 kg/ha (Vectolex). En-tomological evaluations included larval surveysand adult collections conducted inside or outsidehouses of the area with ultraviolet-updraft lighttraps. Because bioinsecticide applications weremade mostly in slow-running waters where larvaeof An. pseudopunctipennis prevail, larvicidal effectpersisted less than 7 days for both products. How-ever, this was sufficient to sharply reduce the num-ber of mosquitoes for more than 14 days after ap-plication of larvicide, especially in the VectoBacarea. We concluded that the application ofVectoBac could be a good complement to suppressmosquito larvae in this area, where environmentalmanipulation of filamentous algae, the primarysource for An. pseudopunctipennis breeding, hasbeen very successful.

Preliminary evaluation of indoor housespraying of biphenthrine l0 WP on

Anopheles albimanus in malarious areas ofChetumal, Quintana Roo, M6xico

Marco A. Dominguez-Galera, Mario Urzua,Adriana E. Flores-Suarez and

Ildefonso Fernandez-Salas

Programa de Control de Vectores, Secretaria deSalud, Mdxico; and Laboratorio de Entomologia

Medica, Facultad de Ciencias Biologicas, Univer-sidad Aut6noma de Nuevo Le6n, San Nicolas de

los Garza, Nuevo Le6n, Mdxico

Studies of the residual effects and behavioralchanges of Anopheles albimanus to biphenthrinewere conducted in 5 localities near Chetumal City,

Ssp.rsN4srR. 2002 Moseurro Vsc'ron Covrnol AND BroI-ocy n.{ LAT[{ Ar,rpntca-A TWELFIH SrTr.posruv t4 l

Quintana Roo State, in southern M6xico from Julyto September 2001. Wall bioassays to determine re-siduality showed lOOTo morlality after 15 and 30days after treatment when a Hudson X-pert back-pack was utilized, whereas 94.7Vo mortality result-ed when fast spraying was done with low-volume-dispensing backpacks for the same periods. Humanlanding mosquito collections showed ranges of 1-5 bites/human/h indoors compared to 10-24 bites/human/h outdoors. Temporal changes of female agestructure of An. albimanr.t showed a reduction inparity from 54 to 2IVo. Endophilic behavior of in-door-resting females also was assessed. We foundmosquitoes in only 7 of 94 sprayed houses, with atotal of 8 An. albimanas; however, after 24 h theywere all dead. All 8 females had ovaries in Sella'sstages I or 2, suggesting that they were freshly fed.A Colombian curtain was set to measure repellencyand irritability to biphenthrine and both behaviorswere recorded. Female Ae. albimanus rested on bi-phenthrine-sprayed walls for a 2-h prefeeding pe-riod inside the experimental house and tried to exitat least 2 h after feeding. A group of 560 field-collected mosquitoes were released and only lOVotried to escape. These individuals had IOOVo mor-tality after 24 h.

Integrated control of Anopheks albimanuslarval populations in southern Chiapas, M6xico

Juan I. Arredondo-Jim€nez,Kenia M. Vald6z-Delgado and

Mario H. Rodrfsuez

Centro de Investigacfon de Paludismo, InstitutoNacional de Salud Prtblica, Tapachula, Chiapas,

M€xico; and Centro de Investigaciones Sobre En-

fermedades Infecciosas, Instituto Nacional de Sal-ud Pfiblica, Cuernavaca, Morelos, Mdxico

We are investigating the integrated control of lar-val Anopheles albimanus and its impact on thenumber of biting adults in neighboring villagesalong the coastal plain of Chiapas, M6xico. Tacticsbeing evaluated separately or together, and beingapplied as needed, include environmental manage-ment (i.e., elimination of vegetation that favorsbreeding and elimination of puddles within villagesdue to tire tracks, open sewage canals, and so on),all with strong community participation; applicationof Bacillus sphaericus (Vectolex@ CG) with a mistblower at rate of I g/m2/sec; and application of lar-vivorous fis}l^ (Poecilia sphenops) only in artificialwater collections (e.g., irrigation canals, drainagecanals, roadside ditches, and large puddles due torecurrent tire tracks on the streets of villages) atrates of 150 fish,/ha. All these tactics were com-pared with an untreated control. Tactics are beingapplied in all breeding sites situated within a 2-kmradius around the villages. Evaluations includeweekly larval surveys and indoor-outdoor adult

collections (landing counts and ultraviolet-updraftlight traps). Thus far, >80Vo and 2507o reductionsof larval and adult populations of An. albimanus,respectively, have been obtained by integrating allcontrol tactics compared to untreated locations.

Biology of Triatoma Picturata(Hemiptera: Reduviidae) under

laboratory conditions

Jose Alejandro Martinez-Ibarra,Maria del Rosario Hernandez-Robles,

Yunuen Grant-Guillen and Monica Novelo Lopez

Area de Entomologia Mddica, Centro Universitar-io del Sur, Universidad de Guadalaiara,

Jalisco, Mdxico

Triatoma picturata is one of the most importantvectors of Chagas Disease in M6xico. In westernM6xico, T. picturata is commonly found in humanhabitations, chicken coops, and in some sylvatichabitats. The biology of this species is poorly un-derstood, in spite of its active domestication, fre-quent contact with humans, and high Trypanosomacruzi infection rates. Taking into account previousinformation on the host preference of T. picturata,the objective of this study was to understand its lifecycle, number of blood meals required before molt-ing, and parameters related to vectorial capacity ofa triatomine species fed on leghorn hens under lab-oratory conditions. Time until feeding began, timerequired to get a complete meal, and defecation pat-terns were recorded. Specimens were separated ingroups of 12 lst-stage nymphs, placed in plasticcontainers (10/container), fed weekly on leghornhens, and checked daily for molting and mortality.The mean time for the life cycle was 165 -t 6.7days, with fewer than 10 blood meals needed formolting 5 times from lst instar to adult. All stages,including adults, began feeding within 5 min andwere in contact with the host less than 5 min. First,3rd, and 5th nymphal instars and adults defecatedsoon (less than 5 min) after feeding. With the shortlife cycle, aggressiveness, and rapid defecation be-havior of T. picturata, it can be considered an im-portant vector of T. cruzi to humans.

Control of the black salt-marsh mosquitoOc hl.erotatus tae niorhynchzs at the

Panama Canal

G. Davila de Obaldia, R. Chang, L. De Le6n,R. Carrasco and V. Youns

Panama Canal Authority, Panama,Republic of Panama

Ship transits through the Panama Canal requiremore than 30 h. Annoyance by mosquito bitesrepresents one of the main complaints of discom-fort by the Canal's labor force. Unusually high

142 Jounn,rL op rHe Avrenrca.t Mosqurro CoNrnol Assocr,crroN Vor-. 18. No. 3

tides and rains in salt-marsh areas near the Canalin May 2001 increased the populations of theblack salt-marsh mosquito (Ochlerotatus taenior-hynchus). The nuisance produced by largeswarms of this mosquito and its role in the trans-mission of Venezuelan equine encephali t is viruscompelled us to double our efforts and treat thismosquito problem as an emergency situationwithin our interagency pest management pro-gram. Efforts stressed physical control throughditching and draining of swampy areas, mainte-nance of tide gates, and chemical control withlarvicides and adult icides. In addit ion, recom-mendations for the use of long-sleeve shirts andrepellents on exposed areas of the body, and theinstallation of mosquito screens on doors andwindows, as well as curtains in shop doors, wereissued. In I month, we managed to reduce thenumber of black salt-marsh mosquitoes collectedin New Jersey light traps from 2,500 to less than100 mosquitoes per trap night.

Aquatic Diptera of the Pesqueria River:entomological risks of polluted waters

V. A. Rodriguez-Castro, H. Quiroz Martinez,A. Ali, F Gonzi4lez-Jimdnez,A. Escalera-Arredondo and

R. Maldonado-Cruz

Laboratorio de Entomologia, Facultad de Cien-cias Biokigicas, Universidad Aut6noma de Nuevo

Le6n, San Nicolds de los Garza, Nuevo Le6n,Mdxico; and Mid-Florida Research and Education

Center, Apopka, FLPolluted waters are ideal breeding sites for sev-

eral species of aquatic insects, especial ly thoseincluded as r-selected; among them several spe-cies can be an entomological r isk to humanhealth. Our objective was to identify the aquaticDiptera of Pesqueria Riveq one of the most pol-luted aquatic systems in Nuevo Leon State. Threesquare meters of the bottom of this aquatic sys-tem were taken from 6 study sites along the Pes-queria River. An entomological net was intro-duced after the substrate was removed and theorganisms were transferred into the net. All in-sects were preserved in ethyl alcohol and iden-tified. A total of 116,076 Diptera larvae were col-Iected in 10 sample dates. These were from 9families that included Chironomidae, Ceratopo-gonidae, Culicidae, Psychodidae, Strat iomyidae,Tabanidae, Muscidae, Syrphidae, and Ephydri-dae. The dominant species was Chironomus plu-mosus (99.73Vo). We also found Culex pipiens,

Cx. interrogator, Cx. erraticus, Anopheles pseu-dopunctipennis, and Chrysops sp.

Serologic survey of arboviruses in LacandonForest area from Chiapas, M6xico

Armando Ulloa. N. Komar.J. D. M6ndez-S6nchez, J. I. Arredondo-Jimenez,

S. Langevin, A. Powers, D. J. Gubler andC. Villarreal-Treviflo

Centro de Investigaci6n de Paludismo, INSP, Ta-pachula, Chiapas, Mdxico; and Division of Vector

Borne Infectious Diseases, Centers for DiseaseControl and Prevention, Fort Collins, CO

A serologic survey in domestic animals (birdsand mammals) was conducted in 5 communities inthe Lacandon Forest, Chiapas, during May 28-June2, 2001, with the objective of identifying arbovi-ruses circulating in this area. We collected serafrom healthy domestic chickens, domestic geese,domestic ducks, domestic turkeys, horses, and cat-tle. The samples were tested by plaque-reductionneutralization test for antibodies to West Nile, west-em equine encephalomyelitis, eastern equine en-cephalomyelitis, Venezuelan equine encephalitis(VEE), St. Louis encephalitis (SLE), and Ilheus andBussuquara viruses. Neutralizing antibodies to SLEwere detected in 2 (2Vo) of 9l chickens,2 (1Vo) of27 turkeys, 16 (247o) of 67 cattle, and 3 (6OVo) of5 horses. Antibodies to VEE were detected in 27(4OVo) of 67 cattle and | (2OVo) of 5 horses. Noneutralizing antibodies against the other viruseswere detected, although cross-reacting flavivirusantibody was detected in a single cattle specimen.Our results of arbovirus activity are the I st reportedfrom Chiapas.

Preventing dengue: the Nuevo Leon VectorControl Program model in

northeastern M6xico

Jorge A. Chiu-Garcia andMa. Teresa Gonzalez-Mendoza

Dengue Vector Control Program, Nuevo Le6nHealth Department, Monterrey,

Nuevo Le6n, Mdxico

Dengue fever is considered a priority for publichealth authorities in Mdxico. Disease incidence isaccentuated in urban areas because of the indoor-resting behavior of Aedes aegypti. Control expertsbelieve that the most important dengue preventionmeasure will be attained by promoting communityparticipation, and an efficient education program tochange human behavior is under way. However,chemical control interventions need to be conduct-ed when outbreaks appear. In M6xico, when im-portant dengue epidemics occur, vector controlmeasures with short-term duration are applied. InNuevo Le6n State, short-term and simultaneousprevention interventions were applied in 2000 and

2001. In other words, we acted as though an emer-

SEPTEMBER 2002 Mosourro VEcroR Covrnol AND Brorocy rN LnrrN Avsruca-A Tweu.nr Svr{Posruut 143

gency had occurred, when none existed. The suc-cessful prevention model redlrced cases from11.000 in L999 to 25 and 10 cases for 2000 and2001, respectively. The latter were confirmed byenzyme-linked immunosorbent assays in the statelaboratory. Our experience led us to build a pre-vention model based on epidemiological and ento-mological history. In Nuevo Le6n State, monthlydengue frequency was detected in August and Sep-tember (higher rainfall and fall-like temperaturesfavoring vector longevity) when the lst outbreaksappeared. Considering virus extrinsic and intrinsicincubation periods, earlier cases started occurringin July and August. These months coincided withthe summer vacations of university students andtheir increased travel activity. Similarly, we foundthat house indices of Ae. aegypri increased in Juneand peaked in July. These data came from 2 yearsof entomological monitoring. We decided to inter-vene in 3-month cycles throughout the year. Inthese activities, we visited 600,000 houses to checkand eliminate breeding sites and covered 30,000blocks with ultra-low-volume space-spraying. As aresult, the house index was reduced to 5Vo in Jtne,July, and August. Similarly, larval indices werelowered more than 6Vo below significant epidemi-ological values. We summarized our model in thefollowing way: analysis of historical epidemiolog-ical and entomological data may help launch inten-sive, short-term, integrated adult and larval controlmeasures in a timely manner to prevent risky vec-tor-dengue--environment situations effi ciently, andtherefore avoid or reduce dramatically dengue out-breaks during the peak transmission season. Wealso agreed that community participation in themidterm would have the highest impact on controlof Ae. aegypti.

Baseline space treatments of Aqua-reslinSuper@, Anvil@, and Solfac@ for the control of

Aedes aegypti

Juan I. Arredondo-Jim1nez andNorma E. Rivero

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Pfiblica, Tapachula,

Chiapas, Mdxico

We studied the efficacy of space treatments of 3insecticides for the control of the dengue virus vec-tor Aedes aegypti. Insecticides tested were water-based Aqua-Reslin Super@, and mineral oil-basedAnvil@ or Solfac@, applied at rates of ll, 6, and 2g/ha, respectively, with London@, HP@, or Micro-gen@ pumps mounted on vehicles. Studies includedstandard linear tests situating sets of 2 cages with20 F, mosquitoes held on T:poles at 2O, 4O,60, 80,and 100 m; and house tests situating sets of 2 cagesholding 20 F, mosquitoes on the front porch, livingroom, bedroom, and backyard. Exposure times

were 30 and 60 min, respectively, for the lineartests and house tests. Overall results indicated thatmineral oil-based insecticides (Anvil and Solfac)were more effective than water-based insecticide(Aqua Reslin-Super). Effective average mortality(>75Vo) in linear tests was observed up to 8O m inAnvil and Solfac tests, whereas 69Vo mortalitycould only be observed at 4O m in Aqua Reslin-Super tests. In house tests, Anvil yielded mosquitomortalities >85Vo in the front porch, living room,bedroom, and backyard. Therefore, Anvil per-formed better than the other insecticides evaluatedto control Ae. aegypti in Chiapas, M6xico.

Impact of insecticide space treatments onAedes aegypfi adult population of Tapachula,

Chiapas, M6xico

Juan I. Arredondo-Jiminez and Norma E. Rivero

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Pfiblica, Tapachula,

Chiapas, Mdxico

To determine whether the dengue virus vectorAedes aegypti is controlled by space treatments ofinsecticide, we assessed the impact of 3 insecticideproducts, Aqua Reslin-Super@, Anvil@, and Sol-fac@, in 7 experimental sets of 9 blocks in Tapa-chula, Chiapas, M6xico. Insecticides were appliedon I or 2 consecutive days during each of 3 fort-night rounds at rates of 11, 6, and 2 glha for AquaReslin-Super, Anvil, and Solfac, respectively. En-tomological impact was assessed by ovipositionrates, number of eggs per ovitrap, house index foradults, and mean number of adults per housethroughout the trial. Results indicated that ovipo-sition rates were not reduced by any of the treat-ments compared with the control, perhaps becauseof input of mosquitoes from surrounding untreatedhouses. However, the mean number of eggs per ovi-trap, house index for adults, and mean number ofadults per house was significantly reduced in theAnvil area with respect to the control, followed byAqua Reslin-Super and Solfac. Comparing l- or 2-day consecutive treatments, no differences were ob-served in the Anvil area. Therefore, although pop-ulations of Ae. aegypti were not eliminated byultra-low-volume treatments, significant reductionswere observed after 1-day application of Anvil.

Susceptibility of Aedes aegypti larvae toorganophosphates and synthetic pyrethroids

insecticides in Nuevo Leon, M6xico

Adriana E. Flores, Gustavo Ponce G.,Mohammad H. Badii, Ildefonso Ferndndez-Salas

and Rafl Torres Z.

Laboratorio de Entomologia Medica, FCB-Univ-ersidad Autdnoma de Nuevo Le6n, San Nicolas de

los Garza, Nuevo Ledn, Mdxico

The Nuevo Le6n State, in northeastern M6xico,officially reported 4,769 cases of dengue fever in

144 JounNlL oF THE AMERIcet Mosqulro Covrnol AssocranoN Vor . 18 , No.3

1999; 32.5Vo of all cases reported in M6xico. Thisis the lst study to document the susceptibility ofhistorically used insecticides against the denguevector, Aedes aegypri in Nuevo Le6n State. Meanlethal concentrations (LCros) in natural mosquitolarval populations from dengue-endemic cities weredetermined. The chemicals evaluated were mala-thion 5OVo, temephos 50 7o, permeth nn 9 5 .92Vo, andbifenthrin 93.25Vo. Bioassay methods followed the1981 World Health Organization standard protocoland results were analyzed by probit analysis. TheLCrn results for malathion were 0.326, O.lOl , 0.247 ,O.2O7, 0.176, and 0.209 ppm for the cities of Mon-terrey, San Nicoli4s, Villa de Santiago,.Allende,Guadalupe, and Escobedo, respectively. The LCrnresults for temephos were 0.00016, 0.00058,0.00054, 0.00050, and 0.00072 ppm for the munic-ipalities of Monterrey, Villa de Santiago, Allende,Guadalupe, and Escobedo, respectively. The LC.oresults for permethrin were 1.3 X l0-5, 1.8 X 10-s,and 1.5 X 10 5 for the cities of Monterrey, Gua-dalupe, and Villa de Santiago, respectively. Con-centration ranges of bifenthrin were between0.0001 and 0.00O55, 0.0001 and 0.0004, 0.00015and 0.0005, and 0.0009 and 0.0025 ppm for thecities of Monterrey, Linares, Villa de Santiago, andAllende, respectively.

Adult and larval Aedes aegypti susceptibility tobifenthrin in Nuevo Le6n, M6xico

Gustavo Ponce G.. Adriana E. Flores.Mohammad H. Badii, Ildefonso Ferndndez-Salas

and Ma. Luisa Rodrfeuez-Tovar

Ittboratorio de Entomologia Medica, FCB-Univ-ersidad Aut6noma de Nuevo Le6n, San Nicolas de

los Garza, Nuevo Le6n, M4xico

Dengue control has been hampered in M6xicoand other Latin American countries by increasingresistance to commonly used chemical insecticides.Resistance has extended to most toxicologicalgroups, including organochlorines, organophos-phates, and synthetic pyrethroids. The absence of adengue vaccine or preventive medications increasesthe importance of mosquito control activities.Therefore, the search for new and more efficientchernicals has become an important activity forvector control programs in developing countries.This study was conducted to assess the susceptibil-ity and resistance of Aedes aegypti to bifenthrin(O.lEa), a pyrethroid recently approved by theWorld Health Organization (WHO) and the M6xicoVector Control Program. We evaluated this newchemical on mosquito populations in 4 dengue-en-demic cities in northeastern M6xico. The WHObioassay methodology for adult mosquitoes wasused. Susceptibility results showed IOOVo mortalityafter 24h on Ae. aegypti from Guadalupe, Allende,Apodaca, and Villa de Santiago. Likewise, the me-

dian lethal time with O.l7o bifenthrin was 36.73min for the entiie mosquito female population.Analysis of our data indicated that bifenthrin couldquickly replace traditionally used adulticides incampaigns against Ae. aegypti. However, more re-search is needed to evaluate potential cross-resis-tance and use of bifenthrin as a new tool for inte-grated vector control programs.

Preliminary field evaluation of Bistar 1.57oULV,(bifenthrin) against the dengue vector

Aedes aegypn- in Allende, Nuevo Le6n, M6xico

Jorge A. Chiu-Garcia,Ma. Teresa Gonzalez-Mendoza,

Adriana E. Flores-Suarez, Gustavo Ponce-Garciaand Ildefonso Fern6ndez-Salas

Dengue Vector Control Program, Nuevo Le6nHealth Department, Monterrey, Nuevo Le6n, Mdx-ico; and Laboratorio de Entomologia Medica, Fa-

cultad de aiencias Biol6gicas, Universidad Au-t4noma de Nuevo Le6n, San Nicolas de los

Garza, Nuevo I*6n, Mdxico

The decision of M6xico at the end of the 199Oswas to ban malattrion for control of adult populationsof the dengue vector Aedes aegypti; this decision wassupported by strong suspicions of resistance to thisorganophosphate, which had been used for 30 years.Consequently, this motivated control programs tosearch for altemate adulticides for use against vectorpopulations because of the increasing ptrblic healthproblem caused by dengue viruses. Bifenthrin (Bis-tap 1.5 ULV) in an oil-based formulation, a syntheticpyrethroid recently introduced in M6xico, was eval-uated in the field. Study sites were established in Al-lende, 50 mi east of Monterrey. A field test was con-ducted in the residential area Colonia Los Perales,which has 2-level concrete houses. Adulticide effec-tiveness was determined through ultra-low-volume(ULV) space-spraying against indoor and outdoorcages of female Ae. aegypti. A total of 20 nylon meshcages measuring 30 X 15 cm contained laboratory-reared, 3-day-old female Ae. aegypti. Ten cages wereplaced in each of 2 inhabited houses in typical indoorand outdoor resting places for this species, such askitchen, living room, dining room, under beds, clos-ets, gardens, backyards, and laundry. Bistar 1.5 ULVwas sprayed at a flow rate of 2.5 oz/min with a 2-nozzle Typhoon II vehicle-mounted.UlV generator,driven at 10 mph. Teflon-coated slides measureddroplet size averaging 20.5 pm. More than 877o ofdroplets were between the ranges of 15 and 25 p.m.Wind speed was less than 2 mph, and ambient tem-perature and relative humidity were 25"C arrd 917o,respectively. Two cages with 2O mosquito€s eachwere set as controls about lO mi away from the studysite. Mortality was recorded at t h alter treatrnent,and total mortality was recorded at24h. Mean indoorand outdoor mortality at '24 h was 7 5.27o; indoor mor-

SsparEvesp 2002 Moseurro VEcroR Cowrnol AND BIoLocY [\t LATIN Alrettc.q-A Twelrnr Snaposrulr 145

tality was lttgtrer (7870) as compared to outdoors(72Vo). T\e highest mortality (887o) was found in liv-ing rooms, whereas the lowest mortality (6OVo) wasfound in kitchen areas. Outdoor sites produced only687o mortality. Control cages had 2Vo mottalrlty. Weconclude that bifenthrin (Bistar 1.57o ULY) is a po-tential tool for control programs against Ae. aegypti,however, more research is still needed to improve ef-fectiveness, including testing slightly higher flowrates.

Preliminary identification ofacetylcholinesterase gene (AceR) in

Aedes aegypti from L0 ecological settings ofVeracruz State. M6xico

M. Hayd6 Loaiza-Becerra, Adriana E. Flores,Norma Gorrochotegui-Escalante,

William C. Black IY Ildefonso Fernandez-Salasand Barrv J. Beatv

Loboratorio de Entomologia Medica, FCB-Univ-ersidad Aut6noma de Nuevo Le6n, San Nicolas de

los Garza, Nuevo Le6n, Mdxico; and AIDL-Mi'crobiology Department, Colorado State Universi-

ty, Fort Collins, CO

The target site of the organophosphate and car-bamate insecticides is acetylcholinesterase (AChE),a serine esterase that hydrolyzes the neurotransmit-ter acetylcholine. Once these insecticides inhibitAChE, paralysis or death of the insect occurs. Twomechanisms confer high resistance to organophos-phorous insecticides: increased detoxification byoverproduced esterases and insensitive AChEs.These mechanisms have been described in manyinsect species. Normal and insensitive AChEs aretransmitted as monofactorial characters (Ace gene).Formal genetics studies have shown 2 AChE forms:a normal form coded by allele Aces and a forminsensitive to inhibition coded by AceR. The use ofmalathion to control mosquitoes in M6xico duringthe last 22 years has selected for those mechanismsand it is obvious that after decades of prolongeduse, selection pressure has been exerted on naturalmosquito populations. The latter effect also hasbeen augmented by concurrent use of the samechemicals for agriculture pests. To conduct researchon population genetics of resistance, field strains ofAedes aegypti were selected to be used as referencestrains in the laboratory. This study evaluated re-sistance mechanisms and therefore usefulness of or-ganophosphorous and other insecticides for denguefever vector control in M€xico. In August 2001,larval sampling of Ae. aegypti was carried out from10 localities in Veracruz State, southeastern M6xi-co. Larvae were transported to the Laboratory ofMedical Entomology at the University of NuevoLe6n for rearing. A polymerase chain reaction-based method was used to detect AceR in the ge-nome of single mosquitoes. The distribution of the

AceR is reported in Ae. aegypli from northern tosouthern Veracruz, M6xico.

Population genetics of Anopheles albimanus inLatin America using microsatellite markers

Ana Marfa de M6rida

(Jniversidad del Valle, Guatemala City, Guatemala

Anopheles albimanus, one of the main vectors ofmalaria in Latin America, has a wide geographicaldistribution and a variable phenotype that makes itessential to evaluate the structure of its populations.Proper identification combined with epidemiologicaland transmission studies can improve malaria control.Four microsatellite markers (MSl-90, MS2-14, MS6-41, and MS2-25) were used to establish the popula-tion structure and phylogenetic relationships of An.albimnnus in Latin America. Mosquitoes were col-lected in 9 countries, with a total of 30 collectionsand 1,412 individuals. After extraction of DNA fromindividual mosquitoes, microsatellite markers wereamplified by polymerase chain reaction. The genotypefor each locus was determined for individual mos-quitoes in polyacrylamide sequencing gels. The mark-ers MS1-90, MS2-14, MS2-25, and MS6-41 present-ed 23, 25,39, and 13 alleles, respectively. In ananalysis of variance of genotype frequencies in 5 re-gions (Cuba, M6xico to Nicaragua, Costa Rica-Pan-ama. Venezuela, and Colombia), 89.917o of total var-iation in allele frequency arose among individuals incollections, whereas only 1.557o of variation aroseamong collections in groups and 8.55Vo of variationarose among groups or regions. The fixation index forthe regions was estimated at 0.085. The results sug-gest partial genetic isolation with respect to CentralAmerica especially of Venezuelan and Colombianpopulations.

Presence of large genetic distsnces inAedes aegypfi populations on M6xicots

Pacific coast

Francisco Garcia-Franco,Marfa de Lourdes Mufroz, Saul Lozano-Fuentes,Ildefonso Fernandez-Salas, Barry J. Beaty and

William C. Black IV

Departamento de Genetica y Biologia Molecular,CINVESTAV-IPN, Distrito Federal, Mdxico; La-

boratorio Entomologia Mddica, Facultad de Cien-cias Bioldgicas, Universidad Aut6noma de Nuevo

Le6n, San Nicolds de los Garza, Nuevo Le6n,Mdxico; and Department of Microbiology, Colo-

rado State University, CO

A population genetic analysis was conductedamong 20 populations of Aedes aegypti from 19cities along the southern Paciflc coast in the statesof Guerrero, Oaxaca, and Chiapas of M6xico andin Coatepeque, Guatemala- Markers included 131

t46 JounNer- oF THE AMERTCAN Moseurro CoNrnol Assocrar.roN Vo l . 18 , No . 3

random amplified polymorphic DNA (RAPD) lociamplified by polymerase chain reaction. Regressionanalysis of geographic distances and pairwise Fstestimated from RAPD markers indicated that pop-ulations are isolated by distance. Furthermore, clus-ter analysis of Fst/(l - Fst) failed to group collec-tions by geographic proximity and as much geneticvariation was found among collections within a 60-km radius as was found among all collectionsthroughout the approximately 9OO-km range. Thislarge genetic differentiation found in southerncoastal M6xico may be due to reduced gene flowarising through reduced human commerce and agreater diversity of habitats and altitudes amongcollection sites.

Protection of Aedes aegypti eggs in commonbreeding sites from M6rida, Yucatdn, M6xico,

during dry periods

J. E. Garcia-Rej6n, L. E Flores-Flores,M. A. Lorofro-Pino, B. J. Beaty and

J. A. Farf6n-Ale

Laboratorio de Arbovirologia, Centro de Inve.rti-gaciones Regionales "Dr. Hideyo Noguchi,"

Universidad Aut6noma de Yucatdn, Mlrida, Yuca-tdn, Mdxico; and Arthropod Borne and InfectiousD isease s lttborato ry, Microbiolo gy Department,

Coktrado State University, Fort Collins, CO

Aedes aegypti is the vector of dengue viruses inthe Yucati4n Penfnsula of M6xico. Mosquito breed-ing sites frequently are small water containers dis-tributed indoors and outdoors. Mosquito eggs areresistant to desiccation and can remain viable forlong periods of time. When the rainy season begins,eggs hatch and adult populations increase rapidly.Adult mosquito abundance depends in part on theprotection that the container's microenvironmentprovides for the eggs during the dry season. Theobjective of this study was to evaluate the capacityof selected container breeding sites in M6rida toenhance survivorship of eggs of Ae. aegyptl duringthe dry season. This study was conducted from Jan-uary to July 2000. Eggs were obtained from a col-ony of Ae. aegypti from M6rida and collected onpaper strips containing about 100 eggs each. Thestrips were placed inside organdy bags. Six bagswith 3 strips each were placed inside 6 differentcontainers: aluminum can, tire, glass bottle, plasticvessel, ceramic flower pot, and concrete water con-tainer. One bag was collected from each containerand from the insectary (control) after periods of 15,30, 60, 90, l2O, and 150 days. Every strip was im-mersed in a plastic vessel containing 20 ml of wa-ter. The number of emerged larva was recorded at12- 24- and 48 h. Larvae were transferred to con-tainers with 100 ml of water. The proportion ofadults that successfully emerged was determinedfor each container type. Most of the containers pro-

vided environmental conditions that protected theeggs during the dry period; the proportions ofadults that successfully emerged from these con-tainers were similar to the control. However, theproportions of adults that emerged from plastic bot-tles and concrete water containers were significant-ly reduced compared to the control. This suggestedthat these types of containers do not protect mos-quito eggs against desiccation.

The lethaf effects of Eugenia melanadenia andPsidium rotundatum on Aedes aegypti

Lucita Aguilera, Agustin Navarro,Juan E. Tacoronte, Maria C. Marquetti,

Maureen Leyva, Avilio Bello andMaria T. Cabrera

Instituto de Medicina Tropical "Pedro Kouri,"Facultad de Quimica, Universidad de la Habanu,

La Habana, Cuba

Dengue is a mosquitoborne disease for whichthere is no vaccine, and mosquito control consti-tutes the principal means of preventing this disease.The larvicidal effect of certain plants has been rec-ognized as an environmentally safe vector controloption since ancient times, although it is seldomexploited. Commercial larvicides are expensive, in-accessible, and have limitations on their use; there-fore, plant extracts represent an attractive controlalternative. In an effort to discover novel com-pounds with biological activity against larval Aedesaegypti, we conducted laboratory assays with es-sential oils obtained from leaves from 2 Cubanplants in the family Myrtaceae (Eugenia melana-denia and Psidium rotundatum) by a hydrodistil-lation method. Plant assays were replicated 3 timesand each test had at least 4 concentrations. Percentmortality was registered at 24 h after each appli-cation. Results analyzed by probit-log softwaredemonstrated that essential oils had a larvicidal ef-fect, with median lethal concentration and 957o le-thal concentration values of 0.00857o and O.O104Vo,respectively, for E. melanadenia and O.OO63Vo andO.OO7lVo, respectively, for P. rotundatum. Dtagnos-tic concentrations with values of O.OO22Vo and0.Ol64Vo for E. melanadenia and P. rotundatum,respectively, also are provided. The possible impli-cations of these findings on field populations ofAe.aegypti are discussed.

Larval control of mosquitoes withMac rocyclops albidus (Copepoda: Cyclopoidae)

under laboratory conditions

Silvia Suarez, Jinnay Rodriguez,Zulerna Menendez, Agustin Navarro and

Israel Garcia

Departamento de Control de Vectores, Institutode Medicina Tropical "Pedro Kouri,"

La Habana, Cuba

Predatory cyclopoid copepods have been usedsuccessfully in some countries for controlling mos-

SerrcNlepn 2002 Moseurro VEcron CoN'rnol eNo Bror-ocv rN LerrN Ammca-A TwELFI'H Svvposruu t47

quitoes inhabiting both artificial and natural con-tainers. For the lst time in Cuba, we evaluate thepredatory activity of Macrocyclops albidus on lar-vae of Aedes aegypti and Culex quinquefasciatus,mosquitoes that fiequently cohabitate domesticcontainers in urban areas. Experiments were per-formed under laboratory conditions at 25 + 2oCand a 12:72 h light: dark cycle. Plastic 7-liter con-tainers with 5 liters of dechlorinated water and 3 gof leaf litter were used. Two combinations of pred-atory densities (10 and IOO M. albidus) and 3 com-binations of prey densities (3OO Ae. aegypti and OCx. quinquefasciatus, 150 of each species, and 0Ae. aegypti and 300 Cx. quinquefosciatus) werereplicated 5 times. Separate controls with no co-pepods and the same 3 combinations of mosquitodensities were studied in similar containers. Sur-viving larvae and remaining copepods were count-ed 6 days after the experiment began. Analysis ofvariance showed a significant reduction of mosqui-to larvae in all the treatments with copepods. Pred-atory activity was greater on larval Ae. aegypti, andthis effect was not affected by the association withCx. quinquefosciatus.

Ecological diversity of the aquatic insectsassociated witll Culiseta inornata

(Diptera: Culicidae) breeding sites

F. Gonz6lez-Jim6nez, H. Quiroz Martinez,J. I. Gonziilez-Rojas, V. A. Rodriguez-Castro,A. Garcia-Garza and V. A. Gonzrilez-Robledcr

Lctboratorio de Entomologfu, Facuhad de Cien-cias Biol6gicas, and Laboratorio de Ornitologia,

Facultad de Ciencias Biol6gicas, Universidad Au-t6noma de Nuevo Lerin, San Nicolds de los

Garza, Nuevo Lerjn, Mdxico

The knowledge of, the aquatic insect communi-ties that live in breeding sites of Culiseta inornatacould help develop the appropriate strategies tocontrol this species. We evaluated the diversity ofthe aquatic insects in breeding sites with Cs. inor-nata rn San Antonio Pefra Nevada (an ecotourismarea). Each month from July 2000 to June 2001,we took 10 samples from permanent pools with anentomological net and the insects were identified,and their densities were compared on the basis ofindices of Simpson, Shannon, Taylor, and Green.We found a total of 3l genera and species in 5orders; Diptera was the most important, with 7 spe-cies. Maximum diversity with the Simpson indexwas DV : 14.6763 at 2,111 m elevation; the min-imum value was DV : O.43ll at 3,542 m. Thehighest value for the Shannon index was H' :1.0399, this aquatic system was at 1,860 m; thelowest Shannon index was H' : O.43ll at 3,560m. The majority of distribution index was an ag-gregate distribution of 74.19Vo for Thylor and58.33Vo for Green of the total taxa collected.

Larval habitats of Aedes albopi,ctus and itsassociated fauna in Nuevo Le6n, M6xico

Ericka S6nchez, Maria Luisa Rodriguez T.,Ma. Paz Tijerina, Raril Torres 2.,

Adriana E. Flores and Ildefonso Ferndndez S.

Departamento Zoologia Invertebrados, San Nico-lds de los Garza, Nuevo Le6n, Mdxico

Two localities (Allende and Villa de Santiago)have been reported positive for Aedes albopictus inNuevo Le6n State. Larvae are found most frequent-ly in tires; however, the importance of other breed-ing sites is unknown, as well as the relation of thisspecies to other arthropods in the same habitat.From April to October 2001, monthly collectionswere conducted in Allende and Villa de Santiago.A group of 644 containers was inspected and di-vided into the following categories: 49.6Vo discard-ed tires, 38.OVo flower pots,6.OVo plastic containers,4.0Vo metal containers, O.37o Bromeliaceae plants,0.62 small basins, and 1.2Vo ceramic pots. Resultsshowed that 106 (96.37o) tires,2 (1.87o) Bromeli-aceae; | (O.9Vo) metal container, and I (O.97o) p\as-tic container had larval Ae. albopictus. Several oth-er mosquito species (Aedes aegypti, Culex pipiens,and Toxorhynchites rutilis) were also found inbreeding sites of Ae. albopictus.

Influence of the blood-meal source on thedevelopment of Triatoma longipennis

(Hemiptera: Reduviidae)

Yunuen Grant-Guillen andJose Alejandro Martinez-Ibarra

Laboratorio de Salud Piblica, Centro Universi-tario del Sur, Universidad de Guadalajara,

Guadalajara, Jalisco, Mdxico

Triatoma longipennis is among the most impor-tant vectors of Trypanosoma cruzi (Chagas Dis-ease) in M6xico because ofits occurrence in housesand chicken coops, frequent contact with humans,and high T. cruz.i inf'ection rates in villages of west-ern M6xico. As with some other triatomine species,T. longipennis usually feeds on mammals or birds,depending on the availability of the hosts. Studiesof some Triatoma species (e.9., T. infestans, T.brasiliensis, T. sordida, and T. pseudomaculata)have shown that specimens fed on mammals (mice)have shorter developmental times and lower mor-tality rates than those fed on birds (pigeons). Withthe information on the host preference of T. lon-gipennis, the objective of this study was to deter-mine the influence of the blood-meal source on thelife cycle of T. longipennis, number of blood mealsneeded before the molting, and reproductive devel-opment. Specimens were separated in 2 groups of150 lst-stage nymphs, placed in plastic containers(10 each), fed weekly on Winstar rats or leghorn

t48 Jounrqel op rnr AvenrceN Moseuno CoNrnol Assocre.toN VoL . 18 , No .3

hens, and checked daily to record molting and mor-tality. The specimens fed on hens had a shorter lifecycle (mean 209.7 'r 41.8 days) than those fed onrats (259.8 -r 28.7 days), needed fewer meals tomolt, laid more eggs/female after 90 days (mean161.3 -f 5.7 vs. I47.3 + 7.4),but had higher mor-tality rates in each stage. Our results showed that,in contrast to previous studies, the nutritional char-acteristics of blood from hens were higher thanthose of blood from rats. These results support theidea of a strong association of T. longipennis withdomestic birds, as cited in previous studies.

Some cases of myiasis in Nuevo Le6n, M6xico

H. Quiroz Martfnez, V. A. Rodriguez-Castro,F. Gonz6lez-Jim6nez, and L. O. Tejada-Molina

Laboratorio de Entomologfa, Facultad de Cien-cias Biol6gicas, Universidad Aut6noma de Nuevo

Le6n, San Nicohis de los Garza, Nuevo Le6n,Mixico; and Programa de Graduados en Agricul-

tura, ITESM, Monterrey, Nuevo Le6n, Mdxico

The term myiasis was used for the lst time in1840. It has been used to describe the presence ofdipteran larvae in organs and tissue of mammals.Although myiasis frequently has been found intropical zones, several cases have been reported toour laboratory in Nuevo Le6n State. The lst casewas a 70-year-old woman with oestrid larvae in hereyes. The 2nd case was a 33-year-old woman withsarcophagid larvae in her reproductive system (ova-ries). The 3rd case was a 2-year-old girl with acalliphorid larva that suddenly appeared in her re-productive system. These 3 cases are described indetail.

Spatial distribution of Chironomus plumosus(Diptera: Chironomidae) egg masses in a man-

made lake

C. Hern6ndez-Cienfuegos, H. Quiroz Martinez,F. Gonz6lez-Jim6nez, V. A. Rodriguez-Castro,

M. H. Badii-Zabeh and C. Solfs-Rojas

I-oboratorio de Entomologfa, Facubad de Cien-cias Biol6gicas, Universidad Autdnoma de Nuevo

Le6n, San Nicolds de los Garza,Nuevo Le6n, M€xico

Chironomus plumosus is the most commonmidge species in polluted waters in Nuevo Le6nand has been collected throughout the metropolitanarea of Monterrey. To increase our knowledge ofthe oviposition behavior and to improve controlstrategies for this midge, we evaluated spatial dis-tribution of eggs masses in an artificial lake. Weplaced 25-cm2 artificial substrates as ovipositionsites. These were located apart and connected by asynthetic cord. After 24 h of exposure to naturaloviposition, the materials were removed and taken

to the laboratory. Egg masses were counted and thedistribution was analyzed statistically. An averageof 381 egg masses was found per substrate. Wefound no statistical difference between the substratelocations and concluded that female C. plumosusonly need a substrate upon which to lay their eggs.

Effectiveness of Pounce@ 0.4G onMusca domestica larvae

R. Hern6ndez-Cortes, H. Quiroz Martinez,V. A. Rodriguez-Castro, F. Gonz6lez-Jim6nez,

G. Gallegos-Morales andV. Srinchez-Valdez

Laboratorio de Entomologia, Facultad de Cien-cias Biol6gicas, Universidad Aut6noma de Nuevo

Le6n, San Nicolds de los Garza, Nuevo Le6n,Mdxico; and Departamento de Parasitologia,

Universidad Autdnoma Agraria Antonio Narro,Coahuila, Mdxico

As a lst step in the treatment of water enteringsewage treatment plants, solid materials such asplastic, wood, and gravel are removed. All othersolids are covered by organic matter and becomeideal breeding sites for several species of Diptera,where the dominant species has been Musca do-mestica. We evaluated the efficacy of Pounce@ 0.4Gto control larvae of M. domestica under field con-ditions. Our test systems were small cages with Ikg of dry gravel (stored for at least 1 day), wetgravel, a mixture of gravel and plastic, and recentlyremoved gravel. A commercial concentration ofPounce was applied to each test system and then10 3rd-stage larvae were added. Mortality was reg-istered at days 7 , 14,21, and 28 after treatment with5 replications and the data were analyzed by anal-ysis of variance. The mortality caused by Pounce0.4G on larval M. domestica was between 72 andIOOVo in all substrates evaluated and statistical anal-ysis showed no difference between treatment andposttreatment time.

Field evaluation of polymer-based granularformulations of Bacillus thuringiensis israelensis

Maria Guadalupe Maldonado-Blanco,Santos Abraham Martfnez-Rodrtguez,

Luis Jesris Galdn-Wong andHumberto Quiroz Martinez

Laboratorio de Microbiologia Industrial, Depar-tamento de Microbiologia e Inmunologia; and I'a-boratorio de Entomologfa, Departamento de 7'ool'

ogia de Invertebrados, Facultad de CienciasBiol6gicas, Universidad Autdnoma de Nuevo

Le6n, San Nicolds de los Garza,Nuevo Le6n. Mdxico

Bacillus thuringiensis israelensis (Bti)

was produced, evaluated, and formulatedextractwith 3

SEPTEMBER 2002 Mosqurro Vacron Covmol euo Brolocv nr LATN Avnruce-A TWELFTH Svrwostutvt 149

polymers (gelatin, acacia gum, and paraffin) and asolar protectant (malachite green). The extract wastested for efficacy with 200-liter plastic containers,previously colonized with mosquito larvae, in arandom square design with 4 treatments, applied ata dose of 13.7 mg/liter. Larval population densitieswere assessed every 3-4 days after treatment, bytaking l0 dipper samples from each treatment, anda test for residual activity was done at days 2l and33 after treatment against laboratory 4th-stage lar-vae of Aedes aegypti. The data showed that the 3Bti formulations, with arbitrary potency of 196.8ITU/mg, were equally effective at 4 and 7 days posttreatment against larvae of Ae. aegypti and Culexsp. The average number of pupae was significantlyhigher in control than in treatment containers untilday 7 after application, but after day ll, no differ-ences were detected. After 2l and 33 days aftertreatment, residual activity produced 59-857o and54-69Vo mortality, respectively, in laboratory-reared 4th-stage larvae of Ae. aegypti in water sam-ples obtained from treated containers.

Scorpions (Arachnida: Scorpiones) from SanAntonio Pena Nevada, M6xico, with notes on

their spatial and elevational dispersal

C. Solis-Rojas, M. Belmares-Perales,H. Quiroz Martfnez, J. I. Gonzalez-Rojas,

W. A. Albeldano-Vazquez and K. Arevalo-Nino

Laboratorio de Entomologia, Facultad de Cien-cias Biologicas, Universidad Autdnoma de Nuevo

Le6n, San Nicolas de los Garza,Nuevo Le6n, Mixico

The region of San Antonio Pena Nevada is lo-cated in Zaragoza, Nuevo Le6n, M6xico. This re-gion is a candidate to become a Protected NaturalArea. It is characterized for having a diverse veg-etation where pine forest predominates. As part ofthe characterization of the flora and fauna of thisregion, monthly collections of scorpions weremade, where sampling (polygons) at different ele-vations of the zone were established. Inside everypolygon, 5 points of samples were taken (circularplots) from June 2000 to June 2001. In this region,a total of 375 specimens with 3 species of scorpionswas found. The most abundant species was Vaejov-is rossamani, with 355 specimens; this species wasdistributed from an elevation of 2.169 m to 3.307m. Diplocentrus ferrugineus was 2nd in abundancewith 12 specimens collected from 2,199 to 2,282m. Finally, 8 specimens of Vaejovis bilineatus werecollected from 1,983 to 2.282 m. We concluded thatspecies diversity was highest in pine forest vege-tation, whereas the largest number of individualswas captured in oak forests.

New breeding places for AnoPhelesin Colombia

V. A. Olano, H. Brochero, F C6rdoba andC. Arevalo

Instituto Nacional de Salud, Bogota, Colombia;Secretaria de Salud del Choco, Quibdo, Colom-

bia; and Secretaria de Salud del Amazonas,Leticia, Colombia

The finding of immature Anopheles mosquitoesin artificial breeding containers is unusual, becausethese mosquitoes usually breed in natural habitatssuch as rain water ponds, lagoons, flsh ponds, bro-meliads, and streams. This study reports primarymalaria vectors in Colombia breeding in artificialcontainers: Anopheles nufteztovari was found in aconcrete water tank in Cimitarra (Santander State)and in a concrete drain in Itsmina (Choc6); An. al-bimanus was found in an underground well in Mofr-itos (C6rdoba State); An. darlingi was reported ina water jar in Hatillo de la Sabana (Magdalena

State) and in an elevated water tank in Cazuarito(Vichada State); and An. punctimacala was foundin a concrete trough, a puddle of water on a con-crete floor, and in a laundry tank in La Tebaida(Quindio State). All of these artificial containershad 4th-stage larvae, which suggests a good adap-tation of these species to these breeding places.These results have been reported previously inBrasil by Carreira in 2001, but not from Colombia.In view of these findings, it is very important toconsider artificial containers in the epidemiologicaland entomological surveillance of malaria becausethese vector species might colonize these and otherartificial breeding sites.

Natural enzootic vectors of Venezuelan equineencephalitis virus in the Magdalena

Valley, Colombia

Cristina Ferro, Jorge Boshell,Abelardo C. Moncayo, Marta Gonzalez,

Marta L. Ahumada, Wenli Kang andScott C. Weaver

Instituto Nacional de Salud, Bogota, Colombia;Center for Tropical Diseases and Department ofPathology, University of Texas Medical Branch,

Galveston. W

Phylogenetic studies indicate that epizootic andepidemic strains of Venezuelan equine encephalitisvirus (VEE) have evolved at least 3 times from anenzootic, subtype ID lineage that occurs in Colom-bia and western Venezuela. To characterize the en-zootic transmission cycle of these epizootic pro-genitors, we incriminated natural mosquito vectorsin a sylvatic VEE focus in the middle MagdalenaValley of Colombia. Modified Trinidad no. l0 trapswere baited with hamsters and placed in the forest,

150 JouRNer- oF THE AMERTCIN Mosqurro CoNrnol AssocrerroN VoL. 18, No. 3

and daily mosquito collections were frozen for lab-oratory analysis. When hamsters died from a VEEinfection, mosquitoes collected from the corre-sponding trap were sorted by species, triturated,and assayed for virus. In 18 cases, a single, initial,high-titered mosquito pool representing the vectorspecies was detected 2-3 days before hamsterdeath, whereas subsequent collections yielded near-ly complete infection, reflecting viremic bloodmeals from the hamster. Vectors incriminated inthis manner included Culex (Melanoconion) vom-erifer (l1 cases of transmission), Cx. (MeI.) pedroi(5 transmissions), and Cx. (Mel.) adamesi (2 trans-missions). These results extend the number of in-criminated enzootic VEE, vectors to 7, all of whichare members of the Spissipes section of the sub-genus Melanoconktn. Our findings challenge thedogma that a single mosquito species generallyserves as the principal enzootic VEE vector at agiven location.

Entomological study in an urban area withmalaria transmission in the Colomtrian

Pacific coast

V. A. Olano, G. Carrasquilla, J. Osorio,F, Mdndez, L. Valderrama and M. Barreto

Instituto Nacional de Salud, Bogota, Colombia;Fundacion FES, Cali, Colombia: Fundacion Cen-

tro Internacional de Entrenamiento e Investiga-ciones Medicas (CIDEIM), Cali, Colombia; Se-

cretaria de Salud del Valle, Cali, Colombia; andUniversidad del Valle. Cali. Colombia

An epidemiological and entomological study wascarried out from June 1993 to May 1995 in urbanand neighboring communities of Buenaventura, themain Colombian port on the Pacific Ocean, whichis highly vulnerable to malaria transmission. Wehave previously reported Anopheles albimanus asthe most frequently collected species in urban are-as, and An. nufieztovari, as the most frequently col-lected species in neighboring communities. We es-timated the sporozoite rate (SR) and entomologicalinoculation rate (EIR) and correlated them withrainfall, mosquito density, and malaria cases. Twoof 2,499 An. albimanus were positive for Plasmo-dium vivax (SR : 0.087o), with 375 and 116 spo-rozoites, respectively. One of the positive mosqui-toes was collected during the peak biting rate in1994, and the 2nd was collected during a similarpeak in 1995. Both mosquitoes were collected inthe urban area between 1800 and 1900 h. An EIRof 10.5 infective bites per person per year was cal-culated. This study increased our knowledge ofvector bionomics, biting habits, behavior, and pre-ferred breeding places to better understand malariaincidence and establish more effective control strat-egies.

Population genomics of dengue susceptibility inAedes aegypti

Norma Gorrochotesui-Escalante

Department of Microbiology, Colorado Stateversity, Fort Collins, CO

We tested the hypothesis that the early trypsingene conditions midgut susceptibility of Aedes ae-gypti to dengue virus. Specifically, could early tryp-sin cleave specific proteins from the surface of thedengue genome necessary for viral attachment tomosquito midgut epithelial cells? Previous researchhas shown that a minimum of 2 genomic regionscontrol dengue susceptibility in Ae. aegyprl. Bosioshowed that alleles at the early trypsin gene sitestrongly cosegregate with dengue midgut suscepti-bility and that no other genes cosegregate with ear-ly trypsin. The early trypsin gene apparently is apart of a unique signal transduction system. Itsfunction may be to taste the incoming meal to de-termine if protein is sufficient to support a gonad-otrophic cycle. If so, the signal transduction path-way activates late trypsin transcription to digest theblood meal. We showed linkage disequilibriumamong segregating sites in early trypsin in Ae. ae-gypti. Presently, we are examining genes, includingthe early trypsin gene, among > 1,000 mosquitoesfrom 38 collections throughout M6xico. We havesequenced the entire early trypsin gene in 52 indi-viduals from Miguel Aleman, the site that presentedthe greatest early trypsin gene diversity. The prim-ers that we used amplify a portion of the gene en-coding amino acids 89-167 of early trypsin. Thisregion contains the active site and all but 1 of theconserved trypsin residues. A Fortran programPGENOME was used to compare genotype fre-quencies among 52 mosquitoes from Miguel AIe-man. Kristine Bennett fed these mosquitoes per oswith blood containing dengue 2 strain JAM1409 todetermine if each mosquito had a midgut infectionbarrier (MIB) and midgut escape barrier (MEB).She demonstrated 3 phenotypes: infected heads(MIB- and MEB-); uninfected heads and infectedmidguts (MIB- and MEB+), and uninfected headsand midguts (MIB+). We compared differences inearly trypsin nucleotide frequencies between mid-gut infected vs. uninfected Ae. aegyptl from M6x-ico (n : I,47O), and between head infected anduninfected (n : l,O7O). We failed to detect anyquantitative trait nucleotides (QTN) for MEB. Weconcluded that single-strand conformation poly-morphism (SSCP) analysis is a sensitive and spe-cific means to assay for single nucleotide polymor-phisms (SNPs) in individual (diploid) genotypes.We have applied population genomics toward iden-tifying a putative QTN in the early trypsin geneassociated with dengue midgut susceptibility in Ae.aegytpi. Although the early trypsin gene does nothave any QTN that segregates with MEB, 1-3

QTNs apparently are correlated to MIB.

SeprrN4spn 2002 MosOurro VEcroR Covrnol AND BIoLocY rN LArr.{ AN,rsRrcA-A TwELF'ru SYMrcsIt]M t 5 1

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